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Starting around 10 a.m., protesters from both the far right and the far left gathered in a park next to City Hall. For the first few hours they stood on opposite sides of a no-man’s land space that police had set up with orange webbed fencing in the park. There were good-natured taunts between the opposing sides initially, but as more and more people arrived—eventually more than 2,000—the exchanges turned into name-calling and jeers. Police were able to temporarily maintain peace because they had confiscated flagpoles, bats, pipes, sticks, knives and other items as people entered the park. Police also positioned themselves in the neutral zone when the shouting got too intense.

By 1 p.m., all semblances of order or peaceful protest were gone. The two sides had moved onto city streets and set upon each other with fists, M-80 firecrackers, and pepper spray. They hurled bagels, soda cans and even dumpsters back and forth as police largely stood by. The policy of the Berkeley Police Department is not to break up small fights as police involvement might result in more violence and injuries. Even so, 20 people were arrested by the end of the day, and 11 protesters reported injured.

As a reporter who has covered Berkeley since 2009, when two journalists and I founded a local news site, Berkeleyside, I have attended numerous demonstrations. Cal students have staged sit-ins at UC Berkeley buildings and Occupy activists occupied the same park in 2011. Black Lives Matter protests in Berkeley extended over five days in December 2014 and dozens were arrested as they surged onto various freeways, stopping traffic. Berkeley police handle, on average, nine large protests a year, according to Officer Byron White, a spokesman.

But what is happening in Berkeley in 2017 is completely different. Instead of protesters rallying against authoritarianism and state power (the Free Speech Movement protested against the University of California’s decision not to let people distribute political materials on campus; the fight for People’s Park was against the university and the National Guard) these are fights among citizens.

I feel like Berkeley has become the ground zero of a new civil war.

The first clue of the ferocity of this fight came Feb. 1, when former Breitbart writer and self-proclaimed “dangerous faggot” Milo Yiannopolous was scheduled to speak at UC Berkeley. While local media had reported the pushback by liberal professors, most everyone was surprised when an army of people dressed in black, their faces hidden by ski masks and bandanas, marched onto campus around 5:00 p.m. and began swinging sticks, setting objects on fire, and attacking pro-Trump attendees.

UC Berkeley cancelled Yiannopolous’s talk and the black bloc or Antifas, as they call themselves, then swarmed through the downtown, looting a Starbucks, and smashing store windows and ATM machines of Wells Fargo, Bank of America, Chase, and Mechanics Bank.

The violence of the riot garnered national attention. Rather than blaming the black-clad protesters for the violence, many on the right blamed UC Berkeley and Berkeley residents for squashing free speech, just yards away from where the original Free Speech Movement began on Sproul Plaza in 1964. President Trump tweeted that maybe funding to UC Berkeley should be cut.

Those on the right called for a response, and organized a Free Speech rally in Berkeley for March 4, prompting anti-fascists group to vow to show up. A few hundred attended and chaos ensued. The vitriol and violence spewed at that rally prompted the Liberty Revival Alliance, a new group created by Rich Black, to call for a “Patriot’s Day” rally for April 15.

The promoters insisted that they sought a peaceful demonstration, and many were, in fact, largely peaceful. And it did look to this reporter that the far left, the black clad demonstrators, initiated much of the violence. But the pro-Trump side also included provocateurs that preach in favor of white racism, gun rights and against immigrants both legal and illegal. Among those at the rally were members of The “Proud Boys,” a right-wing group started by Gavin McInnes that extolls white chauvinism and has called for closing America’s borders and the Oath Keepers, a group of former military and police who have pledged to uphold the Constitution and support gun rights. The founder of Identity Europa, a supremacy group dedicated to the idea of “awakened Europeans,” Nathan Damigo, attended and was captured on video assaulting a woman. (In the same clip, a man wearing a Jesus Will Judge You sweatshirt is kicking someone on the ground). Lauren Southern, a Canadian far-right activist, was a featured speaker and insisted that Berkeley was “infested” with Communists and militant leftists. Several protesters held up anti-Jewish signs such as one reading, “Da Goyim Know.” Others made the “Heil Hitler” salute.

Some of those on the right actively promoted violence. Kyle Chapman, aka Based Stickman, who has been arrested in Berkeley twice in the previous month, advised his followers in a video how to dress for the day he dubbed “The Battle for Berkeley.” He suggested they don helmets, goggles to protect their eyes from pepper spray and shin guards and demonstrated how to make shields and attach flags to long sticks that could be easily wielded as weapons. He even showed off a spiked ring he planned to wear.

Those on the far left issued their own fashion instructions. “For Safety, Security, and Solidarity: wear a white, gray, or black shirt and jacket (layers is best), and blue jeans,” said the flyer. “Bring a bandana and something to cover your head.”

It is more difficult to identify those in the Antifa movement as they cover their faces, tend to keep their personal identities quiet on social media, and eschew talking to the press. They can be identified by the groups calling for action, such as Berkeley Antifa or BAMN, standing for By Any Means Necessary. Their social media postings reveal that their sole intent on Saturday was to stop the pro-Trump and far right groups from even speaking. The notion of allowing an exchange of ideas is anathema to black-block and anti-fascists groups.

Their members believe “fascist white supremacists should not be granted the right to express their views in public,” Mark Bray, a visiting historian at Dartmouth College and the author of Translating Anarchy: The Anarchism of Occupy Wall Street told Brook Gladstone on WYNC’s On the Media.

The result was two camps with fixed ideologies determined not to discuss or debate but to fight one another for dominance. The hatred between the demonstrators could be seen on their faces and at the way they lunged at one another over a six-hour period. Each side was convinced of its righteousness, that it was fighting for the future of America. And at the end of the day, each side declared victory on social media. (If you doubt that is significant, know that these sites and You Tube videos and Twitter streams have thousands, if not hundreds of thousands of followers.)

I have no doubt that there will be another confrontation called for Berkeley in the coming months. Those on the right can’t resist the irony that conservative speech is squashed in the city that launched the Free Speech Movement. The Bay Area is rich with activists and motivating them to confront those they consider racist, fascist, and sexist is easy.

Berkeley has always been on the vanguard, a barometer of the direction the country is going. Not only was this city the birthplace of the free speech movement, it was the first city to put police on bicycles, the first to voluntarily desegregate its public schools, the first to offer equal benefits for domestic partners, and the first to ban Styrofoam.

So the country should be disturbed by the hand-to hand combat among citizens that broke out in Berkeley on Saturday. And be warned.